Measurement of alterations of pulmonary mechanics in guinea pigs is used as a toxicological tool to evaluate response to irritants. Experiments proposed are designed to address gaps in the animal toxicology data of air quality criteria for sulfur oxides and particulates, for ozone, and for oxides of nitrogen. Ozone pre-exposure causes an increased sensitivity to bronchoconstrictive agents such as histamine and serotonin. Studies will be extended to examine the effect of ozone pre-exposure on the degree of response to sulfuric acid, irritant sulfates, formaldehyde, and an organophosphorus insecticide. The effect of ozone pre-exposure and nitrogen dioxide pre-exposure on the response of sensitized animals challenged with antigen aerosols will be examined. Information is needed in this area, but to do such studies on human subjects would raise valid ethical questions. The irritant potency of sodium sulfite aerosols will be assessed. Sulfites are known to occur in the atmosphere, but little is known of their inhalation toxicology. We will also examine the interaction of flame-generated carbonaceous particles (soot). Chemical interactions have been observed experimentally and in the atmosphere, but little is known of their biological action.